Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$165.31	8.591%	$179.5118	$179.51	$179.50	$179.50
Purchase #2	$178.42	6.405%	$189.8478	$189.85	$189.85	$189.80
Purchase #3	$82.43	5.295%	$86.7947	$86.79	$86.80	$86.80
Purchase #4	$113.28	11.105%	$125.8597	$125.86	$125.85	$125.90
Purchase #5	$87.46	11.436%	$97.4619	$97.46	$97.45	$97.50
Purchase #6	$83.71	12.136%	$93.869	$93.87	$93.85	$93.90
Purchase #7	$155.33	8.526%	$168.5734	$168.57	$168.55	$168.60
7 purchase totals =	$865.94		$941.9183	$941.91	$941.85	$942.00